Patent GB-790175-A (GB)
Title: Improvements in or relating to centrifugally operated speed-adjusting devices
IPC: G05D13/00
Filed: 1956-03-23
Abstract: 790,175. Centrifugal governors. SIEMENS & HALSKE AKT.-GES. March 23, 1956 [March 24, 1955], No. 9184/56. Class 57. [Also in Group XXXIV] In a governor for controlling the speed of a driven,shaft 20 by centrifugally operated brake means the tension of the loading springs 45, 46 for the braking shoes 43, 44 is automatically adjusted when the speed of the shaft varies from a set value by separate centrifugally operated control means. The inner ends of the springs 45, 46 are attached to adjusting levers 39, 40 pivotally mounted at 37, 38 and engaging lugs 35, 36 on a bush 33 axially movable in a sleeve 32 but rotatably fixed relative thereto by means of a pin (not shown) in the sleeve engaging an axial slot (not shown) in the bush. The sleeve 32 forms part of a member 21 secured to the shaft 20 and having two axially spaced discs 23 and 24 respectively contacting at their peripheries one half only of the width of cam levers 15 and 16 rotatably mounted on a spindle 14 and carrying pawls 17 and 18 respectively urged by a spring 19 into contact with ratchet wheels 10 and 11 having teeth pointing in opposite directions and secured to a control shaft 9 that is screwed in a threaded bush 8 fixed to the housing 1 and bears against the lower end of a pivoted lever 7 having a slotted upper end contacting a ball bearing 34 in the end of the bush 33. A bell-crank control lever 26 pivoted on a support 25 on the disc 24 has a vertical arm freely surrounding the member 21 and formed at its free end as a cam 27 and a horizontal arm extending through a slot in the disc 23 and connected by a tension spring 31 to a speed-setting lever 30 pivotally mounted on the member 21. A speed-setting screw 4 screwed into a bush 3 in the housing 1 extends through the slotted end of the lever 7 and abuts the lever 30. In operation, when the shaft is running at the set value, determined by the screw 4, the vertical arm of the lever 26 is parallel to the discs 23, 24, the cam 27 passes between the cam lever 15, 16 and the control shaft 9 is stationary. If the speed of the shafts falls, due to an increase in motor load, the spring 31 overcomes the reduced centrifugal force acting on the lever 26 which is thereby turned anti-clockwise and the cam 27 intermittently engages the cam lever 16 to oscillate it about the spindle 14 and turn the ratchet wheel 11, by means of the pawl 17, clockwise as seen in Fig. 2. The control shaft 9 moves to the left, as seen in Fig. 1, and rotates the lever 7 so that the bush 33 is moved axially to the right and the levers 39 and 40 are rotated to increase the tension in the springs 45 and 46 and lessen the braking force until the speed is restored to the set value and the control shaft 9 is again stationary. Similarly, if the shaft speed increases above the set value, the lever 26 is turned clockwise, cam 27 engages cam lever 15 to rotate ratchet wheel 10, shaft 9 is moved to the right, and the bush 33 to the left to reduce the tension in springs 45 and 46 and increase the braking force. The set value of the shaft speed may be adjusted by the screw 4. To limit the amount of movement of the control shaft 9 in either direction, smooth circumferential grooves are provided at the adjacent ends of the ratchet wheels 10 and 11.